Methods for increasing oil production

ABSTRACT

According to a method of recovering petroleum from dormant oil wells or increasing the production of oil wells, an alkali or alkali earth carbonate is introduced into a water layer associated with a subterranean petroleum reservoir and/or an explosive composition is introduced into an oil layer associated with a subterranean petroleum reservoir. CO 2  gas is produced by reacting the alkali or alkali earth carbonate with an acid and/or by detonating the explosive composition. An explosive composition can be introduced and detonated to achieve sufficient CO 2  gas production to increase pressure within the subterranean petroleum reservoir. Petroleum recovery can be further enhanced through the use of recycling.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of priority to ProvisionalApplication Ser. No. 61/347,179 filed on May 21, 2010, which isincorporated herein by reference.

TECHNICAL FIELD

This disclosure relates to revitalization of dormant oil wells andincreased petroleum productions from oil wells by artificialpressurization.

BACKGROUND

Oil wells are formed from boreholes drilled into a porous, subterraneanrock formation containing petroleum. These porous, subterranean rockformations are referred to as petroleum reservoirs or oil reservoirs.Often, a petroleum reservoir is located beneath a less permeable rocklayer that traps the reservoir under pressure. In reservoirs under newlydeveloped production, pressure naturally present within the reservoirprovides force to allow for the migration of petroleum from thepetroleum bearing rock into the borehole forming the oil well. As an oilwell produces, pressure subsides until a point is reached whereproduction is no longer economically sustainable, and the oil well istypically abandoned.

An abandoned oil well can potentially contain over half of the originalamount of oil in the reservoir; however, a lack of pressure in thereservoir makes continued operation of the oil well economicallyunproductive without further intervention. Several secondary andtertiary recovery methods have been used to recover additional oil. Onemethod is to inject water or a gas (such as CO₂ or nitrogen) into thereservoir to create additional pressure. Polymers and surfactants havealso been employed to lower the viscosity of petroleum remaining in thereservoir and aid in petroleum flow. However, such methods are typicallycostly or potentially impractical in cases where materials are expensiveand/or large amounts of water are not locally available.

SUMMARY

The following presents a simplified summary of the invention in order toprovide a basic understanding of some aspects of the invention. Thissummary is not an extensive overview of the invention. It is intended toneither identify key or critical elements of the invention nor delineatethe scope of the invention. Its sole purpose is to present some conceptsof the invention in a simplified form as a prelude to the more detaileddescription that is presented later.

The compositions and methods disclosed herein provide for a low-costrecovery of additional petroleum from sleeping wells as well as enhancedthe petroleum production from active wells in an economically efficientmanner. Pressure in the form of CO₂ gas is generated by detonating anexplosive and by reacting a carbonate or bicarbonate compound with anacid. The acid, typically in the form of a mineral acid, also serves toacidify a water layer or aquifer associated with the petroleumreservoir. The solubility of CO₂ gas in water is reduced at low pH.Therefore, acidification of any water present in the vicinity of thepetroleum reservoir allows a greater fraction of generated CO₂ gas tocontribute to pressurizing the petroleum reservoir rather thanunproductively dissolving into water. A wide range of explosives can beused to practice the methods disclosed herein. The explosive can be asolid, liquid, gel, or a slurry, although free flowing explosives willassist in the introduction of the explosive into the petroleumreservoir. Typical explosive compositions employed in the invention areformed from separate fuel and oxidizer mixed together with a nitrogencontaining organic compound. The explosive can be carbon rich as tomaximize CO₂ production and minimize water production during combustion.

One aspect is directed toward methods to increase petroleum productionfrom an oil well drilled into a petroleum reservoir having an oil layerand an aqueous layer. One or more of an alkali carbonate or an alkaliearth carbonate is delivered into the water layer through an injectionwell drilled into the water layer. All wells drilled into the reservoirare sealed in a manner to substantially confine pressure build-up withinthe reservoir. An acid is delivered through an injection well drilledinto the aqueous layer to react with the alkali carbonate or alkaliearth carbonate to generate CO₂ gas. The CO₂ gas can be separated fromthe petroleum and recycled by injecting the separated CO₂ gas back intothe oil well.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a representation of a subterranean petroleum reservoir withwells placed therein in accordance with aspects of the invention.

FIG. 2 is a representation of a subterranean petroleum reservoir withwells placed therein and depicting supplemental recovery methods inaccordance with aspects of the invention.

FIG. 3 is a flow chart of illustrative acts of methods for increasingpetroleum production in accordance with aspects of the invention.

FIG. 4 is a flow chart of illustrative acts of methods for increasingpetroleum production in accordance with aspects of the invention.

FIG. 5 depicts the chemical structures of amidine compounds (FormulaVIII), carboxamidine compounds (Formula IX), quaternary organic ammoniumcompounds (Formula X), and pyrazole compounds (Formula XI) in accordancewith aspects of the invention.

DETAILED DESCRIPTION

Petroleum deposits are typically located in subterranean, porous rockformations wherein the porous rock is overlaid with a less porous rockformation preventing the escape of petroleum to the surface. The layerof less porous rock is often referred to as cap rock. In addition topreventing the escape of petroleum, the cap rock also prevents gasesproduced from the transformation of organic matter into petroleum. Assuch, untapped, virgin petroleum deposits are often under considerablepressure.

The pressure present in untapped petroleum deposits assists in theefficient extraction of petroleum from deposits. An oil well typicallyconsists of a jacketed borehole drilled through the cap rock and intothe petroleum bearing rock. Perforations are formed in the jacket andthe natural pressure within the petroleum bearing rock causes themigration of petroleum into the borehole. The pressure within thepetroleum deposit can be sufficient to create an oil gusher. Largeblowout preventers are often required to prevent overpressure from thepetroleum reservoir from damaging sensitive equipment. As the petroleumdeposit produces, pressure naturally decreases as petroleum is removedfrom the deposit. Often, high pressure is initially maintained due tothe elution of gasses from liquid petroleum or pressure from waterlayers or aquifers located underneath many petroleum deposits. In allsituations, the rate of petroleum production from a well slows overtime.

The rate of production necessary for continued economical operation is afunction of operation costs, taxes and/or royalties, and oil commodityprice. Abandonment of a well is the economically preferable course ofaction when the amount of money made from oil production is below theassociated costs (operation costs and taxes). As oil production slows,it is possible to attempt to increase production through the use ofvarious secondary and tertiary techniques to increase production rate;however, all such techniques also increase operation costs. Secondaryand tertiary techniques are aimed at either increasing pressure withinthe petroleum deposit to increase production rate or to decrease theviscosity of petroleum remaining within the deposit. Injection of waterand/or gas, polymers, and thermally enhanced recovery methods areexamples of common, but often costly, techniques.

The innovations disclosed herein are directed toward the efficientproduction of CO₂ within a petroleum deposit to revive an abandoned wellor to increase production of an existing well. CO₂ pressure isintroduced into a petroleum deposit by means of an explosive engineeredto produce a maximum release of CO₂ within a sealed oil well. Fuel forthe explosive can be provided by materials located on-site at apetroleum production operation, such as unrefined crude oil, tar, andparaffin waxes, which may be more efficiently employed to increaseproduction rate than the value obtained for such materials on themarket. That is, the value of increased petroleum production exceeds theprice of such materials on the open market, thereby, allowing oilproduction to be increased with minimal associated cost.

The methods disclosed herein are directed toward artificial productionof CO₂ within a subterranean petroleum reservoir. One aspect is directedtoward generation of CO₂ gas by addition of an alkali or alkali earthcarbonate compound and a mineral acid to a water layer or aquiferassociated with the subterranean petroleum reservoir and reacting thealkali or alkali earth carbonate with an acid. Another aspect isdirected toward generation by acidification of a water layer or aquiferassociated with the subterranean petroleum reservoir and adding anexplosive composition containing an alkali or alkali earth carbonatefollowed by detonation of the explosive composition. A nitrogencontaining organic compound can be optionally included in any of the CO₂generation formulations. Another aspect is directed toward increasingpetroleum production by creating CO₂ pressure within a subterraneanpetroleum reservoir combined with one or supplemental techniques toreduce petroleum viscosity including sonication and microwave radiation.

Due to the need to generate pressure, the size of the reservoir ispreferably not an overly vast size. In one embodiment, the volume withinthe porous rock of the petroleum reservoir is less than about 10 km³. Inanother embodiment, the volume within the porous rock of the petroleumreservoir is less than about 10 km³. In yet another embodiment, thevolume within the porous rock of the petroleum reservoir is less thanabout 1 km³.

Formation of Explosive Composition

The explosive compositions useful in practicing the invention contain atleast the two following components: a fuel source and an oxidizer. Inanother embodiment, the explosive composition contains a fuel source, anoxidizer, an emulsifying agent and optionally a nitrogen containingorganic compound. In yet another embodiment, the explosive compositioncontains a fuel source, an oxidizer, an emulsifying agent, and an alkalior alkali earth carbonate compound.

In one embodiment, the fuel source can be selected from one or more ofcarbon powder, unrefined crude oil, unrefined crude oil originating fromthe oil well to be revitalized, tar derived from crude oil, refineddiesel fuel, lubricating oil, heavy gas oil, and paraffin waxes. Otherfuel sources can also be used provided that sufficient combustionoccurs. In another embodiment, the fuel source is a carbon powder or a“hydrocarbon-based” compound, or a mixture thereof, wherein the term“carbon powder” refers to amorphous carbon and/or graphite and the term“hydrocarbon-based” refers to compounds formed from primarily carbon andhydrogen. In one embodiment of a hydrocarbon-based compound, thecompound contains no hetero atoms (atoms other than carbon and hydrogen)and can contain alkane, alkene, alkyne, cyclic, or aromaticfunctionalities. In one embodiment, the carbon powder has an averageparticle size diameter from about 20 nm to about 1 mm. In anotherembodiment, the carbon powder has an average particle size diameter fromabout 1 μm to about 500 μm. In yet another embodiment, the carbon powderhas an average particle size diameter from about 50 μm to about 300 μm.In another embodiment, the hydrocarbon-based compound contains no morethan about three hetero atoms per 10 carbon atoms. In yet anotherembodiment, the hydrocarbon-based compound contains no more than aboutone hetero atom per 10 carbon atoms.

The oxidizer component of the explosive can be an inorganic or anorganic nitrate, chlorate or perchlorate. In one embodiment, theoxidizer component is ammonium nitrate. In other embodiment, theoxidizer component is selected from one or more of ammonium nitrate,potassium nitrate, hydroxylammonium nitrate, sodium nitrate, calciumnitrate, ammonium chlorate, sodium perchlorate, ammonium perchlorate andlike nitrate, chlorate and perchlorate compounds. In one embodiment, theoxidizer component is supplied in the form of prills.

In one embodiment, the fuel and oxidizer components can be simply mixedtogether thoroughly to form the explosive composition. However, theexplosive can take the form of a liquid, solid, gel, emulsion or mixturethereof. A free flowing explosive composition facilitates introductionof the explosive into a target subterranean oil reservoir. Formation ofa free flowing explosive composition is facilitated by the formation ofseparate organic/oil phase comprised of the energetic fuel source and aphase comprising the oxidizer, through use of an emulsifying agent. Theoxidizer phase can either be aqueous (water-in-oil emulsion) or formedfrom a water-free molten phase (melt-in-oil emulsion).

Typically, an emulsion is formed by adding an emulsifying agent to thefuel component/phase and mixing until homogeneity. Then, the fuel plusemulsifying agent is added to the oxidizer phase and mixed tohomogeneity. In one embodiment, an alkali or alkali earth carbonate isadded to the emulsion formed from fuel, oxidizer, and emulsifying agentand mixed until bulk homogeneity is achieved. Any additional componentsincluding metallic oxidizers and corrosion resistance compounds areadded to the emulsion containing fuel, oxidizer, and emulsifying agent.In a typical emulsion, the fuel phase forms a continuous phase in theemulsion while the oxidizer and/or aqueous phase forms a discontinuousphase separated from the continuous phase by the emulsifying agent. Thatis, the emulsifying agent forms micro- or nano-sized micelles having aninterior containing the oxidizer and/or aqueous phase. In oneembodiment, the micelles have an average diameter from about 100 nm toabout 1 μm. In another embodiment, the micelles have a diameter fromabout 1 μm to about 100 μm. The small size of the micelles allows fortransport of the micelles into microporous channels within the petroleumreservoir.

Emulsifying agents are amphiphilic compounds having one portion of thecompound being predominately hydrocarbyl in character and anotherportion of the compound being hydrophilic in nature. Useful emulsifyingcompounds include a wide range of amphiphilic compounds including: saltsof carboxylic acids; products of acylation reactions between carboxylicacids or carboxylic anhydrides and amines; and alkyl, acyl and amidederivatives of saccharides (alkyl-saccharide emulsifiers). Salts ofcarboxylic acids can be produced from reacting a largely hydrophobiccompound, containing at least one carboxylic acid functionality, with analkali hydroxide to form a carboxylic acid salt. Products of acylationreactions between carboxylic acids or carboxylic anhydrides and aminescan be produced from reacting a hydrophobic compound, containingcarboxylic acid or carboxylic anhydride functionality, with a primary orsecondary amine-containing compound through an acylation reaction toform an amide. Many carboxylic acid salts suitable for use anemulsifying agent are available commercially, such as sodiummono-oleate, or readily produced from an acid-base reaction between thecorresponding carboxylic acid and sodium hydroxide or similar alkalihydroxide base. Methods for the synthesis of amide compounds are knownin the art, including U.S. Pat. No. 3,219,666, which is herebyincorporated by reference. The hydrophobic compounds useful for reactionwith amines include compounds containing, in addition to at least onehydrocarbyl group, one or more carboxylic acid groups and hydrophobiccompounds that are derivatives of succinic acid, having two carboxylicacid groups, modified with at least one hydrocarbyl group.

The term “hydrocarbyl group” refers to a substituent having largelyhydrocarbon character. That is, the term “hydrocarbyl” as used hereinincludes hydrocarbon as well as substantially hydrocarbon groups.Substantially hydrocarbon describes groups which contain heteroatomsubstituents which do not alter the predominantly hydrocarbon nature ofthe group. Examples of hydrocarbyl groups include hydrocarbonsubstituents, i.e., aliphatic (e.g., alkyl or alkenyl) and substitutedaliphatic substituents, alicyclic (e.g., cycloalkyl, cycloalkenyl)substituents, aromatic-, aliphatic- and alicyclic-substituted aromaticsubstituents, fluorocarbon groups, polysiloxanes, and alkylates.Heteroatoms include, by way of example, fluorine, nitrogen, oxygen,silicon, phosphorus, and sulfur.

In one embodiment, a hydrocarbyl group contains about 1 or more carbonatoms. In one embodiment, a hydrocarbyl group contains about 10 or morecarbon atoms. In another embodiment, the hydrocarbyl group containsabout 10 to about 32 carbon atoms. In yet another embodiment, thehydrocarbyl group contains about 32 to about 200 carbon atoms. In yetanother embodiment, the hydrocarbyl group contains more than about 200carbon atoms. In one embodiment of a hydrocarbyl group, the hydrocarbylgroup contains no hetero atoms and can contain alkane, alkene, alkyne,cyclic, and/or aromatic functionalities. In another embodiment, thehydrocarbyl group contains no more than about three hetero atoms per 10carbon atoms. In yet another embodiment, the hydrocarbyl group containsno more than about one hetero atom per 10 carbon atoms. In still yetanother embodiment, the hydrocarbyl group contains a monounsaturatedalkene functionality and can be oleic acid. Hydrocarbyl groups andcompounds having a hydrocarbyl groups include compositions that arebuilt up from smaller compound. For example, a compound containing fromabout 2 to about 4 carbon atoms can be reacted with an amine or sugar,and then the residue of that compound containing from about 2 to about 4carbon atoms can be added to by polymerization or other chemicalmodification to have a total number of carbon atoms substantiallycongruent with the embodiments described above.

Examples of suitable primary and secondary amines are given by FormulaeI and II, where each R is independently a hydrocarbon group containingfrom about 1 to about 24 carbon atoms. In another embodiment, each R isa hydrocarbon group containing from about 10 to about 20 carbon atoms.H₂N—R  (I)R—NH—R  (II)

Specific examples of suitable primary or secondary amine-containingcompounds include primary monoamines such as methylamine, ethylamine,propylamine, butylamine, octylamine, dodecylamine, and other primaryamines containing from about 1 to about 24 carbon atoms. Examples ofsuitable secondary monoamines include diethylamine, dipropylainedibutylamine, methylbutylamine, ethylhexylamine, and other secondaryamines containing from about 1 to about 24 carbon atoms.

Further examples of suitable primary or secondary amines are given bythe hydroxyl amines of Formulae III and IV and the ether amines ofFormulae V and VI, where R has the same meaning as above, R′ is definedas either an R group or an R group substituted with one or more hydroxylgroups, and x is from about 2 about 15.H₂N—R—OH  (III)R′—NH—R—OH  (IV)H₂N—(RO)_(x)—H  (V)R′—NH(RO)_(x)—H  (VI)

Still further, a suitable primary or secondary amines can be a polyamineas represented by Formula VII, where each R″ group is independentlyeither hydrogen, an R group, or an R group substituted by one or morehydroxyl or amino functionalities, and y is from about 2 to about 10.R″NH—((CH₂)_(y)N)—R₂″  (VII)

The emulsifying agent can also be an alkyl-saccharide emulsifier, whichis herein defined as an alkyl, acyl, ether, carbamide or amidederivatives of a saccharide, which can be a monosaccharide,polysaccharide, or oligosaccharide, formed from a reaction between asaccharide and a compound having a hydrocarbyl group, as describedabove, containing a carboxylic acid, alcohol and/or carbamatefunctionality to from an alkyl, ether, ester, carbamate or amide bondbetween the hydrocarbyl compound and the saccharide. In one embodiment,the alkyl-saccharide emulsifier contains a monosaccharide. In anotherembodiment, the alkyl-saccharide emulsifier contains a saccharide havingfrom about 2 to about 6 saccharide residues. In yet another embodiment,the alky-saccharide emulsifier contains a saccharide having from about 7to about 12 saccharide residues.

In one embodiment, the alkyl-saccharide emulsifier contains amonosaccharide or saccharide residue having from about 4 to about 8carbon atoms. In another embodiment, the alkyl-saccharide emulsifiercontains a monosaccharide or saccharide residue that is an aldose or aketose sugar. In yet another embodiment, the alkyl-saccharide emulsifiercontains a monosaccharide or saccharide residue that is a sugar alcoholsuch as sorbitol and/or the alkyl-saccharide emulsifier can be sorbitolmono-oleate. In still yet another embodiment, the alkyl-saccharideemulsifier contains a monosaccharide or saccharide residue that is adehydration product or a sugar and/or sugar alcohol such as 1,4-sorbitanor isosorbide. In a further embodiment, the alkyl-saccharide emulsifiercontains a monosaccharide or saccharide residue that is an amino sugarsuch as glucosamine. Specific illustrative examples of saccharidesinclude fructose, glucose, galactose, erythrose, ribose, deoxyribose,xylose, mannose, sorbose, sorbitol, 1,4-sorbital, isosorbide,polysorbates, allose, mannoheptulose, octolose and stereoisomersthereof.

In one embodiment, the alkyl-saccharide emulsifier contains about onehydrocarbyl group. In another embodiment, the alkyl-saccharideemulsifier contain from about two to about three hydrocarbyl groups.

Many alkyl-saccharide emulsifiers are available commercially. Inaddition, methods of making saccharide-based emulsifiers having analkyl, ether, ester, carbamate or amide bond between the hydrocarbylcompound and the saccharide are known in the art. WO 97/18243, which ishereby incorporated by reference, describes the synthesis ofsaccharide-based emulsifiers having an ester or amide bond between thehydrocarbyl compound and the saccharide. WO 03/031043, which is herebyincorporated by reference, describes the synthesis of saccharide-basedemulsifiers having an amide or carbamate bond between the hydrocarbylcompound and the saccharide. U.S. Pat. Nos. 5,576,425 and 5,374,715,which are hereby incorporated by reference, describes the synthesis ofsaccharide-based emulsifiers having an ether-type bond between thehydrocarbyl compound and the saccharide.

In one embodiment, the explosive composition contains from about 2% toabout 10% by weight of a fuel component. In another embodiment, theexplosive composition contains from about 3.5% to about 8% by weight ofa fuel component. The fuel component can be the organic phase of anemulsion. In one embodiment, the explosive composition contains fromabout 90% to about 98% by weight of an oxidizer component or an aqueousphase containing an oxidizer component. In another embodiment, theexplosive composition contains from about 92% to about 96.5% by weightof an oxidizer component or an aqueous phase containing an oxidizercomponent. In one embodiment, the emulsifying agent in the explosivecomposition is from about 4% to about 50% of the total weight of thefuel component and/or the organic phase. In another embodiment, theemulsifying agent in the explosive composition is from about 12% toabout 30% of the total weight of the fuel component or the organicphase. In yet another embodiment, the emulsifying agent in the explosivecomposition is from about 4% to about 5% of the total weight of the fuelcomponent or the organic phase.

The explosive compositions and emulsions disclosed herein do not limitthe invention but only serve to illustrate the breadth of explosivecompositions and emulsions useful in the invention. The particularillustrations above represent suitable explosive compositions that maybe efficiently used at a typical oil well site in view of availabilityof components, cost, and ability to generate CO₂ gas.

The above is not exhaustive of the emulsifying compounds useful formaking suitable explosive compositions. U.S. Pat. Nos. 6,800,154;3,447,981; 3,765,964; 3,985,593; 4,008,110; 4,097,316; 4,104,092;4,218,272; 4,259,977; 4,357,184; 4,371,408; 4,391,659; 4,404,050;4,409,044; 4,448,619; 4,453,989; 4,534,809; 4,710,248; 4,840,687;4,956,028; 4,863,534; 4,822,433; 4,919,178; 4,919,179; 4,844,756; 4,844,756; 4,818,309; 4,708,753; 4,445,576; 4,999,062; International PatentApplication Publication WO 96/28436; UK Patent Application GB2,050,340A; and European Patent Application EP 561,600, all of which areincorporated herein by reference, contain teachings regarding suitableemulsifying compounds as well as teachings concerning methods of makingexplosive compositions including ratios of components and additives.

The combination of fuel and oxidizer is selected based on thestoichiometry of a combustion reaction between the fuel component andthe oxidizer compounds forming CO₂ and water as the primary products.The amount of either component typically can vary up to about 15% fromthe amount dictated by stoichiometry; however, some embodiments candeviate further.

In one embodiment, an alkali or alkali earth carbonate is added to theexplosive composition and mixed until homogeneity is achieved. Weightand percentages of fuel component, oxidizer component, and emulsifyingagent referred to throughout this disclosure refer to weight andpercentages of an explosive composition containing only the fuelcomponent, oxidizer component, emulsifying agent and water included inthe oxidizer/aqueous phase. Alkali or alkali earth carbonates and otheradditives, such as metallic oxidizers, can be added to the explosivecomposition by mixing. However, the discussion of weight and percentagesof fuel component, oxidizer component, and emulsifying agent, above, isin reference to the mass of the explosive composition without suchadditional additives.

The alkali or alkali earth carbonate serves as an additional source ofCO₂ gas. Alkali or alkali earth carbonate can decompose into CO₂ gasupon detonation of the explosive composition. Alkali and alkali earthcarbonates include, but are not limited to, sodium carbonate (soda ash),calcium carbonate, potassium carbonate, magnesium carbonate, hydratedcalcium carbonates, hydrated potassium carbonates, hydrated magnesiumcarbonates, hydrated sodium carbonates such as Na₂CO₃.H₂O, Na₂CO₃.7H₂O,Na₂CO₃.10H₂O, sodium bicarbonate, calcium bicarbonate, potassiumbicarbonate, magnesium bi carbonate, hydrated calcium bicarbonates,hydrated potassium bicarbonates, hydrated magnesium bicarbonates,hydrated sodium bicarbonates, Na₃H(CO₃)₂.2H₂O, and Na₂CO₃.NaHCO₃.2H₂O(sequi carbonate).

The alkali or alkali earth carbonate can be supplied as particulatematerial in the micro or nano size range. In one embodiment, the averagediameter of alkali or alkali earth carbonate particles is about 100 μmor less. In another embodiment, the average diameter of alkali or alkaliearth carbonate particles is from about 1 to about 100 μm. In yetanother embodiment, the average diameter of alkali or alkali earthcarbonate particles is from about 500 nm to about 1 μm. In yet anotherembodiment, the average diameter of alkali or alkali earth carbonateparticles is from about 250 to about 500 nm. In still yet anotherembodiment, the average diameter of alkali or alkali earth carbonateparticles is from about 400 nm to about 100 μm. In a further embodiment,the average diameter of alkali or alkali earth carbonate particles isabout 500 nm or less. Throughout this disclosure, micro- or nano-sizedparticles refers particles having one of the preceding diameter sizerestrictions.

Alkali earth carbonates are practically insoluble in water at pH aboveabout 6 and only sparingly soluble at pH from about 4 to about 6.Therefore, particulate alkali earth carbonate can be mixed into anexplosive composition that is an emulsion with minimal loss ofparticulate material due to alkali or alkali earth carbonate dissolvingin water. However, the aqueous phase of the emulsion can be buffered toa pH where carbonate is sparingly soluble or insoluble is needed.

In one embodiment, the alkali or alkali earth carbonate compound isadded to the explosive composition such that the ratio of carbonate toother components is from about 1:10 to about 1:2 by weight. In anotherembodiment, the alkali or alkali earth carbonate compound is added tothe explosive composition such that the ratio of carbonate to othercomponents is from about 1:5 to about 2:5 by weight. In yet anotherembodiment, the alkali or alkali earth carbonate compound is added tothe explosive composition such that the ratio of carbonate to othercomponents is from about 1:5 to about 2:5 by weight.

In one embodiment, the explosive composition contains from about 1% toabout 10% by weight of a nitrogen containing organic compound. Inanother embodiment, the explosive composition contains from about 2% toabout 8% by weight of a nitrogen containing organic compound.

One or more nitrogen containing organic compounds can be optionallyincluded in any of the carbon dioxide generation formulations. Nitrogencontaining organic compounds can stabilize carbon dioxide generationformulations. Particularly when emulsions and temporary emulsions areinvolved, nitrogen containing organic compounds when used can provideincreased stability to the emulsion (that is, increase the duration ofexistence of the emulsion before the emulsion breaks down).

The nitrogen containing organic compounds suitable for optional use inthe carbon dioxide generation formulations described herein have acapability to form cations in water and carbon dioxide. In oneembodiment, the nitrogen containing organic compounds contain at leastabout 10 carbon atoms to facilitate compatibility with oil. For example,in one embodiment, the nitrogen containing organic compounds contain analkyl group with at least about 10 carbon atoms to facilitatecompatibility with the organic phase. In one embodiment, the nitrogencontaining organic compounds can form cations in water. The nitrogencontaining organic compounds can facilitate oil and water to be onephase in the presence of carbonate and bicarbonate ions.

The nitrogen containing organic compounds can stabilize emulsions duringcertain stages in of the methods described herein. The nitrogencontaining organic compounds can also promote the formation of temporaryemulsions, thereby acting as switchable surfactants that use benigngases (CO₂ and air) as the triggers to switch them “on” and “off”.Specifically, on exposure to about an atmosphere of gaseous CO₂,nitrogen containing organic compounds such as amidines mixed with wateror an alcohol react exothermically to form the bicarbonate oralkylcarbonate salts. The reaction can be reversed by bubbling nitrogenor argon through the neat liquid salt, or else through a solution if thesalt is a solid. While not wishing to be bound by any theory, it isbelieved that a nitrogen containing organic compound with an organiccharacter is a poor surfactant but becomes an effective surfactant onconversion to the charged cationic nitrogen containing organic compoundbicarbonate by exposure to water and CO₂. Another benefit of usingnitrogen containing organic compounds is that the product generated byswitching off the surfactant has negligible surface activity and watersolubility, which is a substantial environmental advantage.

Examples of nitrogen containing organic compounds include amidinecompounds, carboxamidine compounds, quaternary organic ammoniumcompounds, and N-hetercyclic compounds (a hetecyclic compound containingat least one nitrogen atom in the backbone). The chemical structures ofamidine compounds, carboxamidine compounds, and quaternary organicammonium compounds are respectively shown in Formulae VIII, IX, X, andXI of FIG. 5. Each R in Formulae VIII, IX, X, and XI of FIG. 5 areindependently hydrogen, alkyl groups containing from 1 to about 30carbon atoms, hydroxy alkyl or alkoxy alkyl groups containing from 2 toabout 30 carbon atoms, aryl groups containing from 6 to about 30 carbonatoms, or hydroxy aryl groups containing from 6 to about 30 carbonatoms. In another embodiment, Each R in Formulae VIII, IX, X, and XI ofFIG. 5 are independently hydrogen, alkyl groups containing from 8 toabout 25 carbon atoms, hydroxy alkyl or alkoxy alkyl groups containingfrom 8 to about 25 carbon atoms, aryl groups containing from 10 to about20 carbon atoms, or hydroxy aryl groups containing from 10 to about 20carbon atoms. Although not shown, the quaternary organic ammoniumcompounds typically have an anion portion ionically coupled with thecationic quaternary organic ammonium portion.

Specific examples of amidine compounds include cyclic and non-cyclicamidine compounds such as guanidine. A general example of quaternaryorganic ammonium compound is a tetraalkylammonium compound where thealkyl groups independently contain 1 to 30 carbon atoms. Specificexamples of quaternary organic ammonium compounds includetetramethylammonium compounds, tetraethylammonium compounds,tetrapropylammonium compounds, tetrabutylammonium compounds,tetra-n-octylammonium compounds, methyltriethylammonium compounds,diethyldimethylammonium compounds, methyltripropylammonium compounds,methyltributylammonium compounds, cetyltrimethylammonium compounds,trimethylhydroxyethylammonium compounds, trimethylmethoxyethylammoniumcompounds, dimethyidihydroxyethylammonium compounds,methyltrihydroxyethylam-monium compounds, phenyltrimethylammoniumcompounds, phenyltriethylam-monium compounds, benzyltrimethylammoniumcompounds, benzyltriethylam-monium compounds, dimethylpyrolidiniumcompounds, dimethylpiperidinium compounds, diisopropylimidazoliniumcompounds, N-alkylpyridinium compounds, etc. Specific examples ofN-hetercyclic compounds include substituted and unsubstitutedpiperidines, imidazolines, pyrazines, pyrazoles, pyridines, quinolines,isoquinolines, bipyridines, picolines, anilinyls, pyrroles, pyrimidines,purines, indolines, azepines, and the like.

Pressurization Through Reaction of Carbonate with an Acid

Referring to FIG. 1, the methods and apparatus of increasing oil wellproduction will be discussed and described. In a typical geologicalformation, an oil reservoir 102 is located underneath a cap 104 ofimpervious rock that prevents petroleum from escaping to the surface.Formation of petroleum within the reservoir 102 displaces water suchthat a typical formation has a water layer 106 located below the lessdense oil layer. A gas cap 108 can form above the oil reservoir 102 andbelow the cap 104, the gas cap can be in situ natural gas or othergasses evolved from the petroleum as petroleum is removed from thereservoir 102, or can be gas artificially introduced. In a typicalformation, bed rock is located below the oil layer 102 and/or waterlayer 106.

A production oil well 110 is drilled from the surface, through the caprock 104, and into a portion of the oil reservoir 102. As describedabove, a well may originally produce oil driven by natural pressurewithin the reservoir with enough pressure to force oil into a storageunit 112. Alternatively, the reservoir can contain enough pressure forthe oil well 110 to produce efficiently, however, a pump 114 can also beprovided to furnish enough energy for oil to complete the journey fromthe oil layer 102 to storage unit 112.

Oil production is increased through the combined use of theCO₂-releasing explosive composition and acidification of the water layer106 and introduction of an alkali or alkali earth compound into thewater layer 106. Components are introduced into the water layer throughan injection well 120 drilled into the water layer 106. More than oneinjection well 120 can be formed to distribute injected componentsthroughout the water layer 106.

In one aspect of the invention, alkali or alkali earth carbonate isinjected through the injection well 120 into the water layer. Theinjection can be with or without pressure as needed. As discussed,alkali earth carbonates are at most only sparingly soluble at pH greaterthan about 4. Therefore, the alkali earth carbonate can be injected asan aqueous slurry. The aqueous portion of the slurry can be buffered tobe slightly basic to prevent formation of CO₂ during introduction ofslurry through well 120. In another embodiment, the alkali or alkaliearth carbonate can be injected as an about saturated solution. In yetanother embodiment, the alkali or alkali earth carbonate can be injectedas a saturated solution in contact with micro- or nano-sized particlesof alkali or alkali earth carbonate. In still yet another embodiment,the alkali or alkali earth carbonate is injected as an about 50%saturated or greater solution. Throughout all methods and innovationsdisclosed, solutions of acids and alkali or alkali earth carbonatesinjected into the petroleum reservoir can contain small amounts ofcorrosion inhibitors to protect metal contact surfaces. For example,Rodine® 213 solutions sold by Henkel Corporation can be used. Rodine®213 is a solution containing substituted keto-amine-hydrochlorides andethoxylated nonylphenols in a base of isopropyl alcohol, propargylalcohol, methyl vinyl ketone, acetone, and acetophenone.

In one embodiment, the slurry of alkali or alkali earth carbonatecontains from about 5 to about 35% by weight of alkali or alkali earthcarbonate. In another embodiment, the slurry contains from about 10 toabout 30% by weight of alkali or alkali earth carbonate. In yet anotherembodiment, the slurry contains about 15 to about 35% by weight ofalkali or alkali earth carbonate.

The alkali or alkali earth carbonate injected into the water layer 106is reacted with an acid to generate CO₂ gas. The acid and carbonatematerial are inject through separate injection wells 120 placed into thewater layer 106. In one embodiment, the alkali or alkali earth carbonateis injected into the water layer before the acid is injected. In anotherembodiment, the acid is injected before the alkali or alkali earthcarbonate is injected. In yet another embodiment, the alkali and alkaliearth carbonate are injected simultaneously. Regardless of the order ofaddition of alkali or alkali earth carbonate, all wells drilled into theoil layer 102 or the water layer 106 must be sealed in a manner tosubstantially contain pressure build-up from the production of CO₂ gas.The acid can be a mineral acid including hydrochloric and sulfuric acid.The acid reacts with the alkali or alkali earth carbonate; the smallsize of the added carbonate assists in the reaction between alkali oralkali earth carbonate and acid to occur quickly and efficiently. Anexcess of acid is used to achieve acidification of the water layer 106,which reduces the amount of CO₂ that dissolves into water and becomesunavailable to contribute the pressure build-up caused by the generationof CO₂ within the reservoir.

As used throughout this disclosure, sealing of wells drilled into theoil layer 102 or the water layer 106 or sealing the reservoir to containpressure is defined to mean sealing one or more of wells 120 and 122 ina manner that does not allow gas to escape. Not all wells 120 and 122need to be physically sealed; only wells necessary to contain pressurewithin the reservoir need to be sealed. In particular, in an embodimentproduction well 110 can remain unsealed since any build-up of pressurewithin the reservoir results in the escape of oil from well 110 ratherthan the escape of gas. Sealing a well also includes attachment of apump to any of wells 120 and 122 for the purpose of introducing anymaterial into the oil 102 or aqueous 106 layers.

In one embodiment, the acid is a mineral acid and is added as solutionthat is about 5 to about 50% concentrated. In another embodiment, theacid is a mineral acid and is added as solution that is about 10 toabout 40% concentrated. In yet another embodiment, the acid is a mineralacid and is added as solution that is about 20 to about 40%concentrated.

Where the alkali or alkali earth carbonate is added to the water layer106 before the acid, the amount of acid addition can be adjusted todepend upon the pH of the water layer 106. The pH of the water layer 106can be monitored through any well 120 that is remote from the well 120through which acid is being added. Water can be either pumped out fromthe water layer 106 and the pH measured or a pH probe may be placedinside a remote well 120. In one embodiment, the amount of acid added issuch that pH in the water layer is from about 4.5 to about 6.5. Inanother embodiment, the amount of acid added is such that pH in thewater later is from about 5.5 to about 6.5. In another embodiment, theamount of acid added is such that pH in the water layer is from about5.5 to about 6. In yet another embodiment, the amount of acid added issuch that pH in the water layer is from about 4.5 to about 5.5.

Acidification of the water layer 106 decreases the fraction of CO₂ thatdissolves in water in the form of carbonic acid. CO₂ that dissolves inthe water layer 106 is unavailable to contribute to pressure increasewithin the reservoir. In one embodiment, from about 50 to about 100% ofthe carbon in the alkali or alkali earth carbonate is released as CO₂.In another embodiment, from about 60 to about 85% of the carbon in thealkali or alkali earth carbonate is released as CO₂. In yet anotherembodiment, from about 35 to about 85% of the carbon in the alkali oralkali earth carbonate is released as CO₂.

Those skilled in the art will readily understand that the fraction ofalkali or alkali earth carbonate reacting with acid to form CO₂ gasand/or carbonic acid is ascertainable through use of pH measurement andthe well-known Henderson-Hasselbalch equation, provided that the waterlayer 106 does not contain any significant buffering agents other thanthe alkali or alkali earth carbonate and enough time has elapsed for thereaction between acid and alkali or alkali earth carbonate to reachequilibrium. For example, the pH of the water layer is approximately5.44 when 90% of the alkali or alkali earth carbonate reacts with twoequivalents of acid based on a pK_(a) of 6.4 for the bicarbonate ion. Inany of the procedures or embodiments disclosed herein, the pH of theaqueous layer 106 can be periodically or continuously monitored toascertain the concentration of acid in the aqueous layer 106.

Due to the large volume of a typical petroleum reservoir, a large timelag can occur between addition of acid and equilibration of the reactionwith the alkali or alkali earth carbonate. Further, the acid can beadded to the water layer 106 before addition of the alkali or alkaliearth carbonate or simultaneous with the addition of alkali or alkaliearth carbonate. Therefore, a predetermined amount of acid can be addedto the water layer 106. The quantity in moles of alkali or alkali earthcarbonate added to the water layer 106 can be readily determined fromthe weight of alkali or alkali earth carbonate added and the molecularweight of that carbonate. Similarly, the equivalents of acid added caneasily be determined by the mass and molecular weight of acid added tothe water layer 106. Hydrochloric acid contains one mole equivalent ofacid per mole while sulfuric acid contains two equivalents of acid permole. In one embodiment, from about 1.5 to about 2 equivalent of acid isadded per mole of alkali or alkali earth carbonate. In anotherembodiment, from about 1 to about 2 equivalents of acid is added permole of alkali or alkali earth carbonate. In yet another embodiment,from about 0.5 to about 1 equivalents of acid is added per mole ofalkali or alkali earth carbonate.

In one embodiment, wells 120 and 122 used to introduce materials intothe aqueous layer 106 and oil layer 102, respectively, are positioned ina manner to minimize the average distance between the wells 120 and 122and production wells 110. This can be achieved by placement of wells 120and 122 in the middle of a group of production wells 110. That is, wells120 and 122 can be position closer to the center of a reservoir relativeto production well or wells 110. In one embodiment, a reservoir has fromabout 1 to about 10 production wells 110 within a distance of about 5 kmfrom either a well 120 or a well 122. In another embodiment, a reservoirhas from about 1 to about 10 production wells 110 within a distance ofabout 1 km from either a well 120 or a well 122.

Pressurization Through Reaction of Carbonate with an Acid In ThePresence of Hard Water

In some regions, the water layer 106 can contain significant amounts ofdivalent cations including Ca²⁺ and/or Mg²⁺. Carbonate ions have apropensity to form a sparingly soluble precipitates in the presence ofCa²⁺ and/or Mg²⁺. As discussed, carbonate can be added to water layer106 is the form of an alkali earth carbonate particulate material in themicro- or nano-size range to avoid the formation of blockages within thewater layer 106. When carbonate is supplied as soluble alkali carbonatein solution, such as sodium carbonate, there is a risk of carbonateforming large precipitates due to reaction with Ca²⁺ and/or Mg²⁺, whichcan impair the flow of materials through the aqueous layer 106 and theporous rock oil layer 102 leading to reduced oil recovery.

To reduce the instances of precipitates forming due to the presence ofCa²⁺ and/or Mg²⁺ ions, a modified procedure of adding carbonate and acidto generate CO₂ gas can be employed. In one embodiment, acid is injectedinto the aqueous layer 106 through an injection well 120, as describedabove, to acidify the aqueous layer 106. Second, acid and acarbonate-containing solution or slurry is injected into the aqueouslayer 106 through separate injection wells 120. That is, an acid isinjected into the aqueous layer 106 through a first injection well 106,and a carbonate-containing solution or slurry is injected into a secondinjection well 120, simultaneously. Acidification of aqueous layer 106prior to the introduction of carbonate allows for the carbonate to reactwith the acid before it is possible for a Ca²⁺- and/or Mg²⁺-containingprecipitate to form. Addition of acid concurrent with the addition ofcarbonate allows for the acidity of the water layer 106 to be maintainedover the course of carbonate addition. The amount ofcarbonate-containing solution or slurry injected into a second injectionwell 120 and the amount of acid injected into the aqueous layer 106through a first injection well can be stoichiometrically matched suchthat the pH of aqueous layer 106, and therefore the rate of CO₂, doesnot vary drastically. That is, once the aqueous layer 106 was adjustedto become acidic, in order to maintain the acidic condition withoutfrequent adjustments, both carbonate solution or slurry and acidsolution can be introduced continuously using two separate pumps throughtwo separate injection wells 120 while the reservoir is sealed toprevent the loss of pressure developed by CO₂ gas. In one embodiment,the acid solution and the carbonate solution or slurry is added at amole ratio of 2:1, such that two equivalents of acid are provided toneutralize one equivalent of carbonate. The pH of the aqueous layer 106can be continuously or periodically monitored to determine if theaqueous layer 106 has sufficient acidity to react with carbonate withoutproducing an excessive amount of precipitate.

In another embodiment, the hardness of the aqueous layer 106(concentration of Ca²⁺ and/or Mg²⁺ ions) is measured using knowntechniques. Acid is injected into the aqueous layer 106 through aninjection well 120, as described above, to acidify the aqueous layer 106such that the molar concentration of acid equivalents (concentration ofH⁺ ions) in the aqueous layer is about two times or more concentratedthan the molar concentration of Ca²⁺- and/or Mg²⁺ ions. In an alternateembodiment, acid is introduced to the aqueous layer 106 such that theconcentration of acid equivalents in the aqueous layer 106 is about fivetime or more than the molar concentration of Ca²⁺ and/or Mg²⁺ ions.After acidification of the aqueous layer 106, a carbonate-containingsolution or slurry is injected into a second injection well 120. Theamount of carbonate-containing solution or slurry injected is a moleamount that is less than the mole amount of acid equivalent introducedinto the well such that the acidity of the aqueous layer is nevercompletely neutralized.

Generally, acid will react will carbonate at a faster rate than of Ca²⁺and/or Mg²⁺ ions. In another alternate embodiment, the amount ofcarbonate-containing solution or slurry injected is a mole amount thatis less than about half the mole amount of acid equivalents introducedto the aqueous layer 106. In still another alternate embodiment, theamount of carbonate-containing solution or slurry injected is a moleamount that is less than about a fourth of the mole amount of acidequivalents introduced to the aqueous layer 106. Those skilled in theart will readily recognize that Ca²⁺ and/or Mg²⁺ ions react withcarbonate by 1:1 stoichiometry to form a precipitate, while two moleequivalents of acid is need to react with carbonate to form CO₂.Therefore in an embodiment, the mole equivalents of acid introduced intoaqueous layer 106 is about twice or more than the mole equivalents ofcarbonate introduced into aqueous layer 106. The addition of acidfollowed by the introduction of CO₂ can be repeated in an iterativeprocess to generate sufficient CO₂ pressure. The pH of the aqueous layer106 can be continuously or periodically monitored to determine if theaqueous layer 106 has sufficient acidity to react with carbonate withoutproducing an excessive amount of precipitate.

Any water used to prepare the acid and/or the carbonate-containingsolution or slurry can be treated to remove Ca⁺- and/or Mg²⁺ ionsthrough the use of cation exchanged resins, distillation, or otherwell-known techniques to deionize water prior to use.

Pressurization Through Use of an Explosive Composition

The explosive composition comprising fuel and oxidant is injectedthrough one or more injection wells 122 drilled into the oil layer ofthe reservoir 102. The explosive composition must be delivered into theoil layer 102 or directly onto the oil layer 102. Alternatively, theexplosive composition can be introduced into one or more productionwells 110. The explosive composition must be placed as to maintaincontact with a primer and a detonator. The primer can be any materialcommonly used to detonate explosives including mercury fulminate, sodiumazide, lead azide, lead styphnate, or tetryl. The detonator can be anelectrical detonator.

The water layer 106 is acidified to minimize loss of CO₂ gas throughdissolution in the water layer 106. In one embodiment, the water layer106 is acidified before addition of the explosive composition to the oillayer 102. In another embodiment, the water layer 106 is acidified afteraddition of the explosive composition to the oil layer 102. In yetanother embodiment, the water layer 106 is acidified simultaneously tothe addition of the explosive composition to the oil layer 102.

In one embodiment, the water layer 106 is acidified to a pH from about 5to about 6. In another embodiment, the water layer 106 is acidified to apH from about 4.5 to about 5.5. In yet another embodiment, the waterlayer 106 is acidified to a pH from about 3.5 to about 4.5.

In one embodiment, the explosive composition is detonated after theaddition of acid is completed. In another embodiment, the explosivecomposition can be detonated before the addition of acid is begun orcompleted. Care must be taken that the explosive blast is not so strongas to damage sensitive equipment at the site, to damage or cause thecollapse of any of the drilled well 120 and 122, or to adversely affectthe subjacent support of the surface terrain. In one embodiment, themagnitude of the explosive blast is the equivalent energy from about0.05 to about 2 metric tons of trinitrotoluene (TNT). In anotherembodiment, the magnitude of the explosive blast is the equivalentenergy from about 0.1 to about 1 metric ton of TNT. In yet anotherembodiment, the magnitude of the explosive blast is the equivalentenergy from about 0.25 to about 1.5 metric tons of TNT. In addition toserving as a source of CO₂ gas, alkali or alkali earth carbonate mixedinto the explosive composition has the additional effect of slowing downthe explosion and cooling the temperature of the explosion as to notdamage the petroleum reservoir formation.

A single explosive detonation can potentially not be sufficient tocreate satisfactory oil production. During both the addition of acid anddetonation of the explosive composition, pressure or rate of oilproduction can be monitored at any well drilled to the oil layer 102. Ifa satisfactory pressure or rate of oil production is not obtained from afirst detonation of the explosive composition, the acts of addingexplosive to the oil layer 102, detonation of the oil layer, andmonitoring the pressure or rate of oil production can be iterativelyrepeated until a satisfactory result is obtained.

CO₂ gas is created through two events utilizing the innovationsdisclosed herein. In the first source, CO₂ gas is created by thereaction between the alkali or alkali earth carbonate and the acid addedto the water layer 106. In the second source, CO₂ gas is created by thedetonation of the explosion through combustion and/or through heatcausing the breakdown of carbonate. The sources of CO₂ gas are referredto as acid generation and explosive generation, respectively. CO₂ can begenerated through acid generation, through explosive generation, orthrough both modes of CO₂ production. Where both acid generation andexplosive generation are employed, the fraction of CO₂ originating fromeither the acid generation method or the explosive generation method canbe modified by varying the amount of explosive composition relative toalkali or alkali earth carbonate injected into the water layer 106throughout all acts of the methods disclosed herein. In one embodiment,the ratio of the weight of carbon contained in the explosive compositionto the weight of carbon contained in the alkali or alkali earthcarbonate is about 0.4 to about 0.6. In another embodiment, the ratio ofthe weight of carbon contained in the explosive composition to theweight of carbon contained in the alkali or alkali earth carbonate isabout 0.2 to about 0.8. In yet another embodiment, the ratio of theweight of carbon contained in the explosive composition to the weight ofcarbon contained in the alkali or alkali earth carbonate is about 0.05to about 0.95.

Recycling

Recycling of carbon dioxide can decrease costs associated with using thepressurization techniques described herein. Crude oil containing carbondioxide that originates from the production well can be directed into agas-liquid separator using suitable separation techniques. Examples ofgas-liquid separators include cryogenic separators, chemical separators(for example, using caustic), condenser separators, a column separator(for example, using a column with packing such as Rashig rings),cylindrical cyclone separators, and the like.

In one embodiment, a single gas-liquid separator is employed to separatea gaseous portion (that is, “off-gas” from the well) containing carbondioxide from the liquid crude. The gaseous portion contains carbondioxide in large part and other components, for example, in the form ofmethane, C2 and C3 hydrocarbons, and residual hydrogen sulfide, if thecrude petroleum product is acidic.

In another embodiment, a first fraction that contains heavy hydrocarbonsand/or liquid hydrocarbons is recovered at the bottom of a firstgas-liquid separator, and a second fraction that contains carbon dioxideand a minor portion of light hydrocarbons is recovered at the top afirst gas-liquid separator. The second fraction can then be compressed,and the compressed second fraction can be circulated in a secondgas-liquid separator in such a way as to separate the gaseous effluentfrom the remaining light hydrocarbons. The second separator can be aconventional separator or a cooling element coupled to the firstgas-liquid separator. The second separator can also be an absorber thatoperates with cooled solvent or a cooled condenser. In this case, thewater that is contained in the gases can be eliminated beforehand if thesecond separator is a cooled condenser.

A single gas-liquid separator or multiple gas-liquid separators areindependently installed at one or more outlets of an oil well.Regardless of whether one gas-liquid separator is employed or multiplegas-liquid separators are employed to collect carbon dioxide, thecollected carbon dioxide is injected into the well to effect recyclingof carbon dioxide. In this connection, the gas flow of carbon dioxide(such as essentially pure carbon dioxide) that exits the gas-liquidseparator can be compressed by a compressor to a suitable pressure levelthat is compatible for injection via an injection well or other means soas to recycle the carbon dioxide.

Alternatively or additionally, the gaseous portion or the off-gas fromthe well is treated to separate carbon dioxide from methane, C2 and C3gaseous hydrocarbons, as the isolated methane, C2 and C3 gaseoushydrocarbons can be collected as a commercial product while the isolatedcarbon dioxide can be subject to recycling.

In one embodiment, carbon dioxide is separated from methane, C2 and C3gaseous hydrocarbons by passing the off-gas through a NaOH solution ofsuitable molarity. The NaOH solution captures carbon dioxide but notmethane, C2 and C3 gaseous hydrocarbons which remain in the gaseousstate. The NaOH solution with captured carbon dioxide forms sodiumcarbonate and sodium bicarbonate that can be pump back into the oil wellfollowed by additional acid addition to subsequently liberate carbondioxide gas within the well to create pressurization. NaOH solutions arecommercially available or a discrete amount of NaOH pellets can be addedto water to make a NaOH solution of desired strength.

In another embodiment, any water is initially removed from the off-gas,and then the off-gas is subjected to cryogenic treatment that serves toseparate the carbon dioxide from the methane, C2 and C3 gaseoushydrocarbons.

The benefits of recycling carbon dioxide are two-fold. First, recyclingcarbon dioxide improves cost-effectiveness of the methods describedherein as a smaller amount of carbon dioxide generation formulations arerequired compared to situations where recycling is not practiced.Second, recycling carbon dioxide is environmentally friendly as theamount of carbon dioxide released into the atmosphere is decreasedcompared to situations where recycling is not practiced.

Supplemental Methods

The methods disclosed herein can be combined with other techniques forthe increased production from a reservoir. For example, the disclosedmethods are directed toward increasing the pressure within a reservoirthrough the production of CO₂ gas. These methods can be combined withoutother strategies for increasing oil production including lowering of theviscosity of oil within the reservoir. In one embodiment, the viscosityof oil in the vicinity of a production well 110 is decreased in order toincrease the rate of production from that production well 110.

One method for decreasing the viscosity of oil is sonication. As shownin FIG. 2, a sonication generator 202 can be provided with an attachedprobe sonicator 204 that can be lowered into a production well 110 to bein contact with oil therein. The size of the probe sonicator is suchthat the bore hole of production well 110 has sufficient diameter toaccommodate the probe sonicator without impeding flow of petroleum fromthe production well 110. Acoustic energy from the probe sonicator canserve to break up any aggregates impeding oil flow near the productionwell 110 as well as generating heat to reduce viscosity. Sonicationmethods can be advantageous in many situations including extraction ofheavy crude and extraction from tar sands. As such, sonication inconjunction with CO₂ gas generation can enhance oil recovery.

Further, thermal methods can be used to decrease oil viscosity byincreasing the temperature of oil neat a production well 110. Anincrease in temperature can also be achieved using microwave techniques.For example as shown in FIG. 2, a microwave generator 206 and amicrowave waveguide 208 can be introduced into a service bore hole 210or into the production well 110 to deliver microwave energy to heat oilin the vicinity of the production well 110. In one embodiment, thewaveguide transmits in the traverse magnetic (TM) mode. In oneembodiment, the waveguide is a hollow waveguide made out of a conductingmaterial such as metal. In another embodiment, the waveguide is a hollowwaveguide made out of a conductive material and filled with a dielectricsubstance.

In order to fully describe the innovations disclosed herein, acts forperforming the inventive method by reaction of acid with alkali oralkali earth carbonate are described by reference to FIG. 2. In act 302,at least one suitable production well drilled into the oil layer of asubterranean petroleum reservoir. In act 304, an alkali or alkali earthcarbonate and/or an acid is injected into the water layer. In act 306,the petroleum reservoir sealed in a manner to substantially contain CO₂pressure throughout the performance of all downstream acts. In act 308,the remaining acts from act 304 are performed if not already executed,at least one injection well drilled into the water layer are identifiedor formed. In act 310, the seal on the petroleum reservoir is sustainedin a manner such that oil can be recovered from a production well. Inact 312, microwave radiation or acoustic energy from a sonication probeis optionally introduced into the petroleum reservoir to reduce theviscosity of the oil within the reservoir. When there is a significantlevel of Ca²⁺ and/or Mg²⁺ ions in an aqueous layer associated with thepetroleum reservoir, injection of acid to the aqueous layer can beperformed before addition of the carbonate to minimize precipitates.

In order to fully describe the innovations disclosed herein, acts forperforming the inventive method by detonating an explosive compositionare described by reference to FIG. 4. In act 402, at least one suitableproduction well drilled into the oil layer of a subterranean petroleumreservoir and at least one injection well drilled into the water layerare identified or formed. Additional injection and/or production wellsdrilled into either the oil layer or the water layer are typicallyprovided. In act 404, the wells drilled into the petroleum reservoir aresealed in a manner to substantially contain pressure. Then, an explosivecomposition is delivered/injected into the oil layer of a petroleumreservoir and/or the water layer associated with the petroleum reservoiris acidified with acid. In act 406, the seal to substantially containpressure within the reservoir is maintained to contain CO₂ pressurethroughout the performance of all downstream acts. In act 408, theremaining acts from act 404 are performed if not already executed. Inact 410, the explosive composition is detonated, and the pressure withinthe petroleum reservoir is monitored and/or the rate of oil productionis monitored. In act 412, microwave radiation or acoustic energy from asonication probe is optionally introduced into the petroleum reservoirto reduce the viscosity of the oil within the reservoir. In act 414,acts of delivering additional explosive composition, detonating theexplosive composition, and monitoring pressure/production are repeated,if necessary. Recycling of CO₂ gas collected by separation techniquesfrom the petroleum can also be employed.

Those having skill in the art will readily recognize that the abovesteps are only illustrative of the inventive methods disclosed herein.When the acts shown in FIGS. 3 and 4 are both performed on the samepetroleum reservoir, the order of act shown in FIGS. 3 and 4 can beperformed in any suitable order to achieve artificial CO₂ gasproduction. For example, an explosive composition can be introduced intothe oil layer and detonated before or after any alkali or alkali earthcarbonate compound is added to the water layer. Those having skill inthe art can readily identify a sequence of acts that lead to successfulCO₂ gas production. The inventive methods are not limited to a specificsequence of acts.

With respect to any figure or numerical range for a givencharacteristic, a figure or a parameter from one range may be combinedwith another figure or a parameter from a different range for the samecharacteristic to generate a numerical range. Other than in theoperating examples, or where otherwise indicated, all numbers, valuesand/or expressions referring to quantities of ingredients, reactionconditions, etc., used in the specification and claims are to beunderstood as modified in all instances by the term “about.”

While the invention has been explained in relation to certainembodiments, it is to be understood that various modifications thereofwill become apparent to those skilled in the art upon reading thespecification. Therefore, it is to be understood that the inventiondisclosed herein is intended to cover such modifications as fall withinthe scope of the appended claims.

1. A method to increase petroleum production from an oil well drilledinto a petroleum reservoir having an oil well drilled into a petroleumreservoir having an oil layer and an aqueous layer having one or more ofCa²⁺ and Mg²⁺ ions present, comprising: delivering an acid into theaqueous layer through one or more injection wells drilled into theaqueous layer; delivering one or more of an alkali carbonate or analkaline earth carbonate into the aqueous layer through one or moreinjection wells drilled into the aqueous layer to generate CO₂ gas;sealing the oil well in a manner to substantially confine an increase inpressure within the petroleum reservoir; recovering CO₂ gas fromrecovered petroleum using one or more gas-liquid separators; andrecycling the recovered CO₂ gas by injecting at least a portion of therecovered CO₂ gas back into the oil well, wherein the mole amount of theone or more of the alkali carbonate and the alkaline earth carbonate isless than half the mole amount of the acid delivered in the aqueouslayer such that the aqueous layer is acidic.
 2. The method of claim 1,the one or more gas-liquid separators comprise at least one selectedfrom the group consisting of a cryogenic separator, a chemicalseparator, a condenser separator, a column separator, and a cylindricalcyclone separator.
 3. The method of claim 1, the one or more gas-liquidseparators comprise an absorber that operates a condenser.
 4. The methodof claim 1, wherein delivering the acid into the aqueous later isperformed before the one or more alkali carbonate or alkaline earthcarbonate into the aqueous layer, and the amount of acid delivered issuch that the molar concentration of H⁺ ions in the aqueous layer isabout two times or more concentrated than the sum of the molarconcentrations of Ca²⁺- and Mg²⁺ ions present in the aqueous layer. 5.The method of claim 1, wherein an alkali carbonate is delivered to theaqueous layer.
 6. The method of claim 1, wherein delivering the one ormore of an alkali carbonate or an alkaline earth carbonate into theaqueous layer is done through a first injection well drilled into theaqueous layer and delivering the acid into the aqueous layer is donethrough a second injection well drilled into the aqueous layer; andwherein at least one delivery of the acid into the aqueous later isperformed before the one or more alkali carbonate or alkaline earthcarbonate is delivered into the aqueous layer, and wherein at least onedelivery of the acid into the aqueous later is performed simultaneous tothe delivery of one or more alkali carbonate or alkaline earth carbonateinto the aqueous layer.
 7. The method of claim 1, wherein the one ormore of alkali carbonate or alkaline earth carbonate is supplied asparticles having an average diameter of about 100 μm or less.
 8. Themethod of claim 1, wherein the alkali or alkaline earth carbonate isdelivered as one or more of an aqueous solution about 50% or moreconcentrated and a slurry having about 5 to about 35% by weight ofalkali or alkaline earth carbonate.
 9. The method of claim 1, whereinthe alkali or alkaline earth carbonate is one or more selected from thegroup consisting of sodium carbonate, calcium carbonate, potassiumcarbonate and magnesium carbonate.
 10. A method to increase petroleumproduction from an oil well drilled into a petroleum reservoir having anoil layer and an aqueous layer having one or more of Ca²⁺ and Mg²⁺ ionspresent, comprising: delivering an acid into the aqueous layer throughone or more injection wells drilled into the aqueous layer; deliveringone or more of an alkali carbonate or an alkaline earth carbonate and anitrogen containing organic compound into the aqueous layer through oneor more injection wells drilled into the aqueous layer; sealing the oilwell in a manner to substantially confine an increase in pressure withinthe petroleum reservoir, wherein delivering the acid into the aqueouslater is performed before the one or more alkali carbonate or alkalineearth carbonate into the aqueous layer, and the amount of acid deliveredis such that the molar concentration of H⁺ ions in the aqueous layer isabout two times or more concentrated than the sum of the molarconcentrations of Ca²⁺ and Mg²⁺ ions present in the aqueous layer suchthat the aqueous layer is acidic.
 11. The method of claim 10, whereinthe nitrogen containing organic compound is selected from the groupconsisting of amidine compounds, carboxamidine compounds, quaternaryorganic ammonium compounds, and N-heterocyclic compounds.
 12. The methodof claim 10, further comprising: recovering CO₂ gas from recoveredpetroleum using one or more gas-liquid separators; and recycling therecovered CO₂ gas by injecting at least a portion of the recovered CO₂gas back into the oil well.